This invention relates generally to elongated composite articles comprising a layer of decorative film on an extruded thermoplastic body and to a method and apparatus for making such articles. More particularly, the present invention relates to decorative trim strips for automotive vehicles and the like and to a method and apparatus for making such trim strips by extruding a thermoplastic body while simultaneously bonding a decorative film strip to at least a portion thereof.
Thermoplastic resin materials can be extruded to form elongated trim strips which can then be used as decorative and/or protective trim for automotive vehicles, appliances and other structures. Trim strips can be attached to exterior or interior surfaces by adhesives or other conventional fastening means and are especially well adapted for use on automotive vehicles, for example, as automotive vehicle side moldings to protect automotive bodies from door strikes while improving the appearance of the vehicle. The appearance of the trim strip itself is often of considerable importance and trim strips of various colors and shapes are known as is the use of a film strip such as a metallic or metallized film strip on at least a portion of the trim strip to present a metallic appearance and to further enhance the aesthetic appeal of the trim strip.
In the manufacture of decorative trim strips with metallized film, the metallized film has generally been laminated to an extruded thermoplastic body by first extruding the thermoplastic body, then securing the metallized film onto a surface portion of the body and then covering the entire outer surface of the film strip and the adjacent areas of base material with a transparent top coat or cover composed of transparent polyvinyl chloride or other transparent thermoplastic material. A top coat or cover over the metallized film is generally necessary to protect the metallized film from the environment. Metallized film usually comprises a thin plastic film sheet such as a polyethylene terephthalate film sheet and an extremely thin layer of metal, such as aluminum, vapor deposited on one or both sides of the film sheet. The initial bright appearance of the metal quickly disappears if it is exposed to weather or corrosive materials. Furthermore, in use, the metal layer can generally be scraped off if it is left exposed and unprotected.
It is not only generally necessary to protect both surfaces of the metallized film, it is also necessary to protect the edges of the film from the environment. Thus, it has generally been the practice to provide a protective top coat over not only the metallized film itself but also the adjacent areas of base material in order to ensure that the edges of metallized film are protected. Unfortunately, this construction is difficult to manufacture, relatively expensive, and results in an undesirably shiny portion of base material, i.e., the areas of base material adjacent to the metallized film coated with transparent top coat. Thus, there is a need for an inexpensive and practical means for providing a trim strip having a metallized film thereon with protected edges obtained other than by top coating adjacent base material.
In accordance with the present invention, a method and apparatus are provided for making an elongated composite article, such as an automotive trim strip or the like, having an extruded thermoplastic body and at least one film strip bonded to a portion of the body. In accordance with the method of the present invention, a thermoplastic body is extruded generally to its desired cross-sectional shape through a longitudinally-extending extrusion passageway in a die assembly. A decorative film strip is simultaneously passed through a guide passageway in the novel die assembly. The decorative film strip is preferably a metallized film which has been topcoated with a protective transparent layer. The guide passageway and the extrusion passageway are separate and isolated from each other but both are in downstream fluid communication with a bonding passageway. Thus, the body and the film strip are passed into the bonding passageway wherein the film strip is bonded to the desired portions of the body. In the bonding passageway, the body expands or swells into contact with the film strip as is bonded thereto, preferably by heat. The bonding passageway preferably has an inlet with a lateral cross-sectional area greater than the combined lateral cross-sectional areas of the extrusion and guide passageways. The bonding passageway also has an outlet which preferably is slightly constricted in cross-sectional area relative to the inlet to facilitate contact between the film strip and body forcibly urging the film strip and body together to increase the bond therebetween. Depending upon the exact structure of the novel die assembly of this invention, the body can expand or swell into bonding engagement with the lateral edges as well as the bottom or inner surface of the trim strip in order to produce a smooth, substantially uninterrupted outer surface or an inlaid effect. Alternately, the base material can expand over lateral edge portions of the top or outer surface of the film strip.
The method and apparatus of the present invention offer many advantages. The present invention facilitates extrusion of hollow or irregular shaped bodies with a metallized film strip on a portion of an outer surface thereof. In accordance with this invention, the edges of a metallized film strip are well sealed against the environment, even where the metallized film strip is flush with the adjacent trim strip surface to provide an inlaid effect. The invention also offers advantages with regard to minimizing tooling components and apparatus required for production of the elongated extrusions and, hence, offers reduced set-up time, start-up time, and down time during production. Additional advantages and features of the present invention will become apparent from the following description and the appended claims taken in conjunction with the accompanying drawings.